Eccentric toothed gearing

ABSTRACT

An eccentric gear transmission, having a rotary drive unit ( 3 ) with an eccentric element ( 8 ), an eccentric wheel ( 10 ) supported rotatably thereon with a set of teeth ( 11 ), which cooperates by intermittent meshing with a set of teeth ( 14 ) of a driver ( 15 ), and furthermore the eccentric wheel ( 10 ) has guide elements ( 12   a;    18, 19 ), which are guided in a stationary housing part ( 6 ) directly or indirectly in receptacles ( 106, 108 ). It is proposed that the housing part ( 6 ) be embodied in one piece, with the receptacles ( 106, 108 ) disposed vibratably in the housing part.

PRIOR ART

The invention relates to an eccentric gear transmission for stepping upthe rotary motion of adjusting motors.

For reducing the rpm of adjusting motors, in which the rotary speed ofthe armature is approximately 7000 rpm, worm gears are as a ruleemployed. These worm gears, which are driven by electric motors, aredistinguished by having self-inhibition from the power takeoff side.Because of the high step-up ratio required to achieve adequate torques,for instance for a power window or power sunroof drive unit in a motorvehicle, the external dimensions of an adjusting motor comprising amotor and side-by-side gears are considerable.

ADVANTAGES OF THE INVENTION

The eccentric gear transmission of the invention having thecharacteristics of the main claim has the advantage of very compactdimensions yet it has self-inhibition and a simple design. Compared withthe known worm gears, the eccentric gear transmission is comparativelyfree of tolerance problems, since all the rotating parts are disposed onone shaft.

An essential component of the eccentric gear transmission is aneccentric wheel, which by its construction can execute two differentmotions. One of these is rolling along a set of external teeth of adriver, which leads to a circular motion about a pivot point that iseccentric to the axis of the eccentric wheel (“swash motion”), and theother is a rotation about itself. The rotation about itself is undesiredand is prevented by guide elements on the eccentric wheel that protrudeinto corresponding receptacles of a housing part solidly joined to thehousing.

The circular motion of the eccentric wheel can be split into two linearmotions perpendicular to one another. In the transmission of theinvention, these two linear motion components are absorbed by a singlepart, while in conventional versions they are absorbed by two separateparts. Because of the one-piece embodiment of the housing part thatabsorbs the circular motions of the eccentric wheel, production costs onthe one hand and the effort and expense of assembly on the other arereduced. Both effects are advantageous.

The particular advantage of the one-piece version of the housing partand the vibratable disposition of the receptacles is that theinteraction between the guide elements of the eccentric wheel and thereceptacles of the housing part takes place entirely without frictionand thus without wear. This guarantees a correspondingly long expectedlife of the eccentric gear transmission of the invention.

Advantageous refinements of the eccentric gear transmission defined bythe main claim are possible with the characteristics recited in thedependent claims.

For instance, the housing part is advantageously made up of threeregions joined together and has an inner region with receptacles, amiddle region, and an outer region joined solidly to the housing; theinner region and the middle region are disposed vibratably relative tothe outer region. The cooperation of the guide elements, mounted on theeccentric wheel, with the receptacles on the inner region of the housingpart brings about the advantageous guidance of the eccentric wheel.

As a result of joining the inner region to the middle region and themiddle region to the outer region via deformable regions, the advantageis obtained that the circular motion of the eccentric wheel about acenter position, which is required for operating the eccentric geartransmission, remains assured.

The advantage of the one-piece design mentioned at the outset isobtained structurally by embodying the deformable regions by means ofrecesses. Thus the complete housing part can be produced in a suitableshape as a single part by injection molding.

An elongated extension of the deformable regions is advantageous becausethen, with minimal stress on the material, the requisite deformation ordeflection of the deformable regions remains assured.

If the deformable regions between the inner region and the middle regionand the deformable regions between the middle region and the outerregion are disposed crosswise to one another, the advantage is obtainedthat the circular motion of the eccentric wheel is separated exactlyinto the two linear components, perpendicular to one another, of thismotion. The resultant forces are thus distributed uniformly to thehousing part and to the deformable regions.

By narrowed portions on the ends of the deformable regions, theirelasticity or spring-constants can be adjusted to suit existingrequirements.

In a further advantageous version of the invention, the housing part ismade up of only two regions joined together, and it has an inner regionand an outer region that is solidly joined to the housing; in this case,the inner region is vibratable relative to the outer region, and thereceptacles are vibratable relative to the inner region.

By joining the inner region to the outer region and by joining thereceptacles to the inner region via deformable regions, the advantage isobtained, precisely as in the first variant, that the circular motion ofthe eccentric wheel about a center position, which is required for theoperation of an eccentric gear transmission, remains assured.

It is especially advantageous in this respect that all of the deformableregions are of equal length and are equally far away from the centerpoint and are thus exposed to an equal stress.

The formation of the deformable regions by recesses, the elongatedextension, and the disposition of the deformable regions that joined tothe receptacles crosswise to the regions that are not joined to thereceptacles all produce the aforementioned advantages.

DRAWING

Two exemplary embodiments of an apparatus according to the invention areshown in the drawing and described in further detail below.

FIG. 1 shows a longitudinal section through an eccentric geartransmission;

FIG. 2 shows a plan view taken along the line II—II of FIG. 1 in thedirection of the arrow A; and

FIG. 3 shows a second exemplary embodiment in a view analogous to FIG.2.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The exemplary embodiment shown in FIG. 1 has an electric motor with aneccentric gear transmission having a shaft 1, which is secured in ahousing bottom 2 in a manner fixed against relative rotation. A drivemeans in the form of an armature 3 is rotatably disposed on the shaft 1and is driven by coils 4 of the electric motor. The coils are disposedon the inside in a cylindrical housing portion 5, and the housing bottom2 is also secured to the housing portion 5. A housing part 6 in the formof a cap with a central opening 7 is solidly mounted on the side of thehousing portion 5 opposite the housing bottom 2. The end of the shaft 1remote from the housing bottom 2 protrudes through this central opening7. The housing portion 5, housing bottom 2 and cap 6 form a motorhousing in whose interior the armature 3 that is rotatable on the shaft1 is disposed, and the eccentric element 8 extending axially along thecenter axis 9 is provided with its eccentric element axis 8A. Aneccentric wheel 10 is rotatably supported on the eccentric element 8 andis provided with a set of internal teeth 11. Two guide elements in theform of two pegs 18, 19 are secured parallel to the shaft 1 on theeccentric wheel 10; they protrude into two receptacles 106 and 108 inthe housing part 6 and are fixed therein.

The internal teeth 11 of the eccentric wheel 10 mesh intermittently witha set of external teeth 14 of a driver 15 that is supported rotatably onthe shaft 1 and secured axially by fastening means 16. The driver 15protrudes through the housing part 6 to emerge from the motor housingand is provided in this region with a further set of external teeth 17for the transmission output.

In FIG. 2, the housing part 6 is shown in plan view; it comprises aninner region 100, a middle region 102, and an outer region 104 joinedsolidly to the housing portion 5. This housing part 6 is the guideelement for the eccentric wheel 10. It is injection molded in one pieceof an elastic material, such as plastic. In its inner region 100, it hasreceiving bores 106, 108 for the two pegs 18, 19. The central opening 7is also disposed on the inner region 100, through which the end of theshaft 1 remote from the housing bottom 2 protrudes. The three regions ofthe housing part 6 are joined integrally to one another via deformableregions 112.

For the sake of better comprehension, the mode of operation of aneccentric gear transmission will be described briefly again here. Bymeans of the magnetic field induced in the coils 4, the armature 3rotates about the shaft 1, which is joined to the housing bottom 2 in amanner secured against relative rotation. Because of the rotation of thearmature 3, the eccentric element 8 also rotates about the shaft 1.

The eccentric wheel 10, supported rotatably on the eccentric element 8,would roll with its internal teeth 11 along the external teeth 14 of thedriver 15, but because of the pegs 18, 19 guided in the receptacles 106,108—it cannot itself execute any rotation about itself, so that thedriver 15, also joined rotatably to the shaft 1, rolls with its teeth 14along the internal teeth 11. Because of this rolling of the driver 15 inthe eccentric wheel 10, the rotary motion of the driver 15 is steppeddown, and this stepped-down rotary motion is carried onward via theexternal teeth 17 of the driver 15.

The eccentric wheel 10 consequently executes a circular motion, leadingto a circular motion of the two pegs 18, 19 that the housing part 6 hasto allow.

This motion can be split into two radial motions perpendicular to oneanother. It is made possible by the deformable regions 112 and effectsthe deflection of the housing part that contains the receptacles 106,108.

The deformable regions 112 are struts, which are formed on both sides byrecesses 114 that are disposed between the regions 100, 102 and 104 tobe joined. In FIG. 2, the recesses 114 have different geometries; themirror symmetry along the two axes II—II and II′—II′, which areperpendicular to one another, is decisive. It is also important that thewidth of the recesses 114 be selected to be at least great enough thatthe deflections of the deformable regions 112 by the eccentric motioncan be received therein, so that the regions 112 are not hindered intheir motion.

By the formation of the recesses 114 in the manner shown in FIG. 2, thedeformable regions 112 between the inner region 100 and the middleregion 102 and the deformable regions 112 between the middle region 102and the outer region 104 are disposed crosswise, or in other words at anangle of 90,° to one another. This arrangement represents an idealgeometry for absorbing the eccentric motion of the eccentric wheel 10.

In FIG. 3, the housing part 6 of a second exemplary embodiment is shown;identical characteristics are provided with the same reference numeralsas in FIG. 2.

The deformable strutlike regions 112 in FIG. 3 are again formed byrecesses 114 on both sides that are disposed between the regions 100 and104 to be joined. In a distinction from the first exemplary embodiment,the second exemplary embodiment has only two subregions 100, 104, andthe two receptacles 106, 108 opposite one another are disposedvibratably not on the inner region 100 but rather on the inner regionvia deformable, beamlike regions 112. This arrangement is crosswise tothe deformable regions 112 that join the inner region 100 to the outerregion 104. Thus here as well, an exact separation of the circularmotion of the eccentric wheel 10 and guidance of it that is advantageousaccording to the invention are achieved.

With regard to the geometry, it is true of the second exemplaryembodiment as well that the paired symmetrical arrangement of the strutsdefined by the recesses 114 is of decisive importance. The width of therecesses 114 must also be selected as great enough to suit thedeflections.

Because of the formation of the recesses 114 as described above, thedeformable regions 112 between the inner region 100 and the outer region104 and the deformable regions 112 between the inner region 100 andreceptacles 106, 108 are disposed crosswise to one another. Thisarrangement represents an ideal geometry for absorbing the eccentricmotion of the eccentric wheel 10.

The two exemplary embodiments of FIGS. 2 and 3 shown can be producedvery simply by an injection molding process; the deformable regions 112can also be provided with inlaid metal parts to increase the strength.

In principle, still other geometries of the recesses 114 areconceivable, for instance leading to deformable regions 112 in the formof an accordion. Regardless of the exemplary embodiments presented, itis important that the subsystems 100, 102, 104 are resistant to relativerotation, and the deformable regions 112 are designed such that they canfollow along with the cyclical motion of the eccentric wheel 10.

What is claimed is:
 1. An eccentric gear transmission, having a rotarydrive unit (3) with an eccentric element (8), an eccentric wheel (10)supported rotatably thereon with a set of teeth (11), which cooperatesby intermittent meshing with a set of teeth (14) of a driver (15), andfurthermore the eccentric wheel (10) has guide elements (12 a; 18, 19),which are guided in a stationary housing part (6) directly or indirectlyin receptacles (106, 108) of the housing part (6), characterized in thatthe housing part (6) is embodied in one piece, and the receptacles (106,108) are formed vibratably in the housing part.
 2. The apparatus ofclaim 1, characterize in that the housing part has an inner region(100), a middle region (102), and an outer region (104) joined solidlyto the rest of the housing, wherein the inner region (100) and themiddle region (102) are disposed vibratably relative to the outer region(104) about axes that are perpendicular to one another.
 3. The apparatusof claim 2, characterized in that the inner region (100) is joined tothe middle region (102), and the middle region (102) is joined to theouter region (104), via deformable regions (112).
 4. The apparatus ofclaim 3, characterized in that the deformable regions (112) are formedby recesses (114), which are disposed between the inner region (100) andthe middle region (102), and between the middle region (102) and theouter region (104).
 5. The apparatus of claim 3, characterized in thatthe deformable regions (112) have an elongated extension, preferablyembodied in beamlike form by recesses (114) disposed on both sides. 6.The apparatus of claim 3, characterized in that the deformable regions(112) between the inner region (100) and the middle region (102) and thedeformable regions (112) between the middle region (102) and the outerregion (104) are disposed crosswise to one another.
 7. The apparatus ofclaim 3, characterized in that the ends of deformable regions (112) havenarrowed portions (116).
 8. The apparatus of claim 1, characterized inthat the housing part has an inner region (100) having the receptacles(106, 108), and an outer region (104) that is joined solidly to the restof the housing, wherein the inner region (100) is disposed as vibratablerelative to the outer region (104), and the receptacles (106, 108) aredisposed vibratably relative to the inner region (100), about axes thatare perpendicular to one another.
 9. The apparatus of claim 8,characterized in that the inner region (100) is joined to the outerregion (104), and the receptacles (106, 108) are joined to the innerregion (100), via deformable regions (112).
 10. The apparatus of claim9, characterized in that the deformable regions (112) are formed byrecesses (114) which are disposed between the inner region (100) and theouter region (104).
 11. The apparatus of claim 9, characterized in thatthe deformable regions (112) have an elongated extension, are preferablyembodied in beamlike form, and are bounded on both sides by recesses(114).
 12. The apparatus of claim 9, characterized in that thedeformable regions (112) joined to the receptacles (106, 108), and thedeformable regions (112) not joined to the receptacles (106, 108), aredisposed crosswise to one another.
 13. The apparatus of claim 9,characterized in that the ends of the deformable regions (112) havenarrowed portions (116).